Ask The Experts
Exterior Finishes

My builder applied TYVEK house wrap underneath the
plywood that is on the exterior walls of my house. I've always seen it
on the outside of the plywood, not behind it. He says it will work as well
underneath the plywood sheathing. Is this true?

Tyvek and other house wraps were designed as air infiltration/exfiltration
barriers. They are intended to prevent air from passing through the myriad
small cracks and gaps in house walls, while allowing water vapor to pass
through, thus lowering your heat bills. House wrap will perform this function
equally well behind the plywood sheathing or on top of the sheathing (directly
behind the siding).

However, house wrap has a second very important function. It helps
shed the water that sneaks through your siding. It can't do that job if
it's buried behind the wood sheathing. Almost all siding types are capable
of allowing water entry. They are never fully sealed. The builders of the
past knew this and used felt paper to help protect the house from this
water entry. Felt paper was very good at shedding water, but wasn't very
good at reducing air infiltration, and can result in condensation build
up in the walls. House wrap is a superior product that can perform both
functions very well if properly installed, directly behind the siding (and
on the outside of the sheathing).

My home inspector discovered that no house wrap was installed
behind the vinyl siding on the house I am buying. I am trying to decide
what, if anything, I should do about it.

In earlier decades most home builders applied a heavy paper, usually asphalt
impregnated felt paper, directly behind whatever siding was being installed
on the house. In the last 30 years or so this has been replaced with a
wider and lighter reinforced paper called housewrap that is water resistant
but breathable. It is being used for the same general purpose as the older
felt paper. It provides an air infiltration barrier for greater energy
efficiency, without potentially trapping condensation, and provides a secondary
barrier against water entry through the siding and into the structure where
it could result in decay. In New York State, the Energy Conservation Code
requires a housewrap when a loose fitting siding such as vinyl is being
applied. Some local builders install the housewrap directly on the framing,
behind the wood sheathing, so it may actually be there, but simply may
not have been visible to your inspector. The problem with this installation
method, however, is that water often does get through the siding, especially
at any openings in the siding, such as windows or doors, meter boxes, the
bottom edge of roof lines attached to side walls, etc., and then becomes
trapped against the wood sheathing, causing decay.

Short of complete removal and reinstallation of the siding with the housewrap
properly installed, which would be very expensive, we recommend that the
areas below any openings be carefully inspected every few years for evidence
of decay. The areas that are most likely to be a problem are those without
effective roof overhangs above. It is fairly easy, in most instances,
to peek behind your vinyl siding at the joints to look for any staining
or wood decay behind, using a good flashlight, or if necessary, by unlocking
the courses with an inexpensive special hand tool designed for that purpose.
If decay is occurring, sections of vinyl siding can be easily removed to
affect repairs, and then be reinstalled, without damaging the vinyl.

Our 1950's house has a “brick-crete” masonry exterior
covered with aluminum siding, except for the lower foot and a half. This
portion is disintegrating. We want to cover this part, but cement plaster
just falls off and fasteners will just cause more damage. What can we
apply to the brick that will hold but won't cause more damage?

Despite your concerns about further damaging the “bricks”, the best bet
probably is to use fasteners designed for masonry, and to secure expanded
steel mesh to the masonry to provide a bonding surface for the cement plaster
or stucco. If the “bricks” are so deteriorated that the fasteners will
not hold, then replacement of the affected masonry may be appropriate.
This does not have to be as daunting as it sounds. If only small sections
are replaced at a time, special support of the masonry above may not be
necessary.

A greater concern with simply applying a cement plaster over the deteriorating
masonry is that you are merely covering up an ongoing problem. Most masonry
deterioration occurs when the material is soft enough to allow moisture
to be absorbed. In our climate, this moisture expands with freezing, and
slowly blows the bricks apart. Good moisture control and drainage close
to the house is essential to prevent further damage. Make sure gutters
are in place and functioning well, that the ground slopes away from the
house, and consider installing crushed stone close to the foundation to
drain any soil in contact with the “brick-crete”.

I have masonite siding on my house, built in 1965. The
siding is deteriorating, especially along the bottom. What's the best
way to repair this siding?

You are probably describing a pre-primed wood product, commonly called
hardboard siding. It essentially consists of pressed and glued sawdust,
formed into ½ inch thick by 11 inch wide boards that usually come in 12
foot lengths. The siding is typically installed horizontally on the house,
with each course lapping the course below, leaving 10 inches of exposed
board. This material is quite vulnerable to moisture and must be kept
well sealed and reasonably protected in order to provide long life. Allegations
of premature failures of this product have resulted in a class action lawsuit
against one manufacturer, Louisiana Pacific. In your case however, the
deterioration can hardly be considered premature. The typical life for
the product is approximately 30 years, so you have done well to get this
far. Any repairs such as patching, filling, and sealing will not be very
effective with this material. Once the swelling and deterioration begins
it is pretty much impossible to stop. You should be able to buy new hardboard
siding to replace the deteriorating sections, as long as the affected areas
aren't too large.

Preventive maintenance is the key to long term success with this siding,
or any other exterior finishes for that matter. Splash damage is the most
likely culprit causing damage to your siding, although poor flashing details
at decks, close proximity or contact with soil, and any other conditions
that result in excess moisture can contribute to the decay. Correction
of any of these conditions should be addressed before replacing the damaged
materials. Splash damage is usually due to missing or poorly maintained
gutters, or missing overhangs. Keeping gutters clean and free of leaks,
and monitoring for bypass, (water sneaking behind the gutters), should
be easy to handle. Missing overhangs can be a bit more difficult to correct.
Many houses built in the 1940s though 1970s did not have good roof overhangs
on the gable ends, and some houses weren't built with good overhangs at
the eaves either. Overhangs can be added to most houses of any age. This
is most cost effectively done when the house is due for a roof tear-off
and replacement. We recommend that overhangs be installed on any house
that doesn't already have them.

My house has aluminum siding on the original part and
vinyl siding on the addition. I would like to paint the siding all one
color. Can I do this and what should I use?

A. Aluminum siding can be very easily painted, and if well prepared
will usually hold the paint longer than wood siding. Vinyl siding is a
little more problematic, but can be successfully painted. We have seen
several homes with painted vinyl siding that look good after five to ten
years of exposure. In either case, using high quality materials and taking
the time to prepare the surfaces properly should ensure satisfactory results.
Preparation involves washing the siding to remove dust, mildew or algae,
and any residue of chalking paint. A power washer can be used, but hand
washing with a detergent and water will work. Be careful using a power
washer to prevent damage to the siding or trim, and to avoid leakage into
the house. Be sure to rinse well so any soap residue will be removed,
and then allow a few days for thorough drying. Because vinyl siding expands
and contracts significantly, you should use a high quality exterior grade
acrylic latex paint, which can stretch with the siding and has very good
adhesive qualities. One word of warning; it is very important that you
paint vinyl with the same or a lighter color than the original vinyl color.
Darker colors will increase the temperature of the vinyl at the hottest
times of year, resulting in permanent buckling or distortion. Anyone who
has left the gas grill a little too close to the siding can attest to its
sensitivity to heat. Some authorities recommend adding special bonding
agents to the paint when applying to vinyl. It may also be helpful to
use a high quality latex primer, since the adhesive qualities of primers
are usually superior to finish paints. It will probably also be wise to
add a mildewcide to the paint. Using an airless sprayer to apply the paint
should result in a more even and professional looking finish, but is not
absolutely necessary.

The vinyl siding on my house has a wavy or puckered appearance,
especially when the sun shines from an angle along the side of the house.
Can this be repaired or does the siding have to be replaced?

The effect that you are seeing is very common and is generally due to
overly tight nailing of the siding to the house, and is usually associated
with a cheaper grade of vinyl. Vinyl siding expands and contracts significantly
with changes in temperature. Vinyl siding is designed with nailing slots
rather than simple holes at the top of each piece of siding to allow for
this movement. If the nails are set too tight, the vinyl can't slide back
and forth at the nails, resulting in buckling of the siding in a tight
pattern that results in the puckered appearance. The siding should be
loosely hung from the nails, rather than being secured to the house. The
siding must also be cut short to allow for expansion, especially if installed
during cold weather. If the vinyl is cut too long, the sections that don't
have room to expand will buckle, even if the nails are sufficiently loose.
Heavier gauge vinyl siding is much less vulnerable to this wavy appearance,
commonly referred to as “oil canning” but proper installation remains
important for good appearance. Vinyl siding is also susceptible to excessive
heat that can result in permanent distortion of the affected surface.
This is usually caused by gas grills being set too close to the siding
during operation, but can also be caused by sunlight reflecting off an
adjacent window. The other process that can result in a poor vinyl appearance
is staining that occurs at nail locations. A chemical reaction that occurs
with the metal of some nails can cause a discoloration that penetrates
through the vinyl. This can sometimes be quite pronounced. None of the
deficiencies that have been included here can normally be corrected without
complete replacement of the affected portions of the vinyl siding. It
is generally easy to remove and replace portions of the vinyl siding, but
getting a good color match for any older siding is virtually impossible.

I am shopping for a home and have heard that EIFS type
stucco finishes are a serious problem. How do I know if the stucco exterior
I'm looking at is this type?

EIFS or Exterior Insulated Finish System can indeed be problematic. It
has been involved in class action law suits due to numerous cases of severe
moisture damage to the exterior wall framing and sheathing behind this
product. In essence, the EIFS stucco finish is applied over a rigid foam
board applied to the exterior of the house. It is a very versatile and
handsome finish that lends itself to very expensive looking architectural
detailing and is becoming increasingly popular.

The problem is that water that enters at openings such as windows, doors,
roof terminations, and other such details, due to poor flashings or seals,
and then becomes trapped behind the finish, causing chronic soaking of
the wood framing and sheathing. Water may enter behind other sidings such
as vinyl in the same manner, but typically drains out, thus reducing the
incidence of decay. The manufacturers have responded by demanding better
attention to flashing details around openings, and in most cases by recommending
the installation of an open weave type drainage mat behind the foam board.

To answer your question though, first be aware that very few homes in
this area have been built with this product (although you can see many
new commercial buildings receiving this finish). Any homes with this finish
are likely to be relatively "high end", (EIFS is not inexpensive),
and the house must have been built relatively recently. If your home doesn't
fall in this category, don't worry.

If the house is recent, identification shouldn't be too difficult.

Since the relatively thin layer of stucco is applied directly over foam,
the finish is quite susceptible to minor impact, so dents, scrapes or cuts
may be noticeable. A light rap with the knuckles should be enough to detect
the slight "give" associated with a product adhered to foam.

You needn't avoid a house with an EIFS finish, but it should be thoroughly
and professionally inspected, and well maintained, if serious problems
are to be avoided.

When I pulled a piece of the aluminum siding off my house,
I noticed that the fiberboard directly behind the siding was quite wet.
Why is this getting wet, and is this normal?

You have asked a very important question about an issue that may negatively
affect many homes over the long run. It is quite likely that the source
of the moisture behind your siding is not leakage, but rather condensation.
We generate large amounts of water in our homes as we cook, shower, breathe,
water plants, and operate humidifiers. Warm air holds the moisture very
well, but cold air does not. As the moisture moves from the warm house
toward the colder dryer outdoors through our walls it reaches the dewpoint
and condenses. There are three ways to reduce this problem. We can reduce
the amount of moisture we produce, we can install a vapor barrier that
reduces the amount of moisture that can make it into the wall, and we can
make it easier for the moisture to get out of the wall, or evaporate to
the exterior.

Unfortunately aluminum is not real good at letting moisture out, so unless
you want to replace the siding, we should look at the other options. Reducing
moisture is usually the easiest task. If you have condensation forming
on many of your windows, the moisture levels are probably too high. We
have addressed excess moisture in previous articles, but look for blocked
or ineffective kitchen, bath or dryer vents, overuse of humidifiers, damp
basements or crawlspaces, blocked gas appliance vents, etc. Install a
permanent dehumidifier, if necessary. It also may be possible to reduce
the moisture transfer into the walls by using a low-permeability paint
on the interior surfaces. This paint acts as a partial vapor barrier.
And make sure that your interior finishes are well sealed. Replaster any
holes, caulk and seal cracks or gaps, and install foam gaskets at switch
and receptacle boxes.

The seriousness of the problem depends on how chronic the moisture is.
Occasional wetting is not a major problem. You don't say if the wet material
was decayed. If not, we suggest taking the measures recommended above
and then monitoring the situation in the colder months. Look for moisture
or stains coming from behind the siding during winter. If the wet material
that you found is moldy or decayed, call in the professionals for a more
thorough investigation.

The wood casings on the exterior of several of my windows
are decaying badly. What should I do to stop this?

You don't say the age of your house, but we'll wager that it was built
since 1950. Modern wood exterior trim, called brick mold, measuring roughly
1 ¼ inch by 2 ¼ inch, generally deteriorates much more rapidly than the
older square cut 5/4 by 4 inch wood trim found on earlier homes. Modern
wood casings are miter cut in the upper corners, which directs water into
the grain of the wood, are often finger jointed, meaning built of numerous
small pieces that allow water entry, and are generally installed without
drip caps at the head casings. In addition, we suspect that the newer
second growth wood we use today tends to be much less rot resistant than
the older wood species found on earlier homes.

Decaying wood trim should not be ignored, because while the trim can
be easily replaced, the wood sills and jambs adjacent to the casings cannot,
and will be next in line for decay if it is not stopped. These parts are
integral to the window or door and are likely to require the replacement
of the entire unit for correction. Decayed wood can be filled and patched,
but this is unlikely to last more than a few years. We recommend that
new wood be installed. The new casings should be primed on all sides before
being installed and should be well sealed, painted and caulked. Preventing
the paint from peeling or wearing out, and repainting as necessary will
go a long way to preventing decay in the first place. Another option is
to aluminum wrap your trim, but this must be very thoughtfully done and
maintained. If water gets behind the aluminum it will be trapped and the
decay will be accelerated. We have found severe decay hidden behind aluminum
trim wrap on many homes in our area. Another way to help prevent decay
is by extending your roof overhangs and maintaining your gutters. This
will help prevent splash damage to your trim. But regular inspection and
maintenance is the key to ensuring the longevity of your wood trim.

I have a 15 year old vinyl sided house with wood trim.
I am finding that a lot of the wood trim is rotting. What can I do to
stop this?

There are several reasons why this wood is decaying, involving poor control
of moisture. Most of the trim wood being used in recent construction is
soft white pine. This wood has low resistance to decay, and must be kept
absolutely dry. One option is to replace the wood with cedar, which has
much better decay resistance. However, it will remain important to keep
any new wood dry by preventing any water from seeping through the exterior
finishes. In a house that is wood sided and trimmed, we do this for the
most part by keeping the finishes well caulked and painted. Vinyl siding,
on the other hand, cannot provide a water tight seal. It is designed,
and should be installed, to readily shed water, but because it expands
and contracts significantly, it must be installed loose and can't be caulked
to provide a seal. When water gets behind the vinyl, which is inevitable,
it should be able to drain back out the bottom. Felt paper or a house
wrap should protect the wood sheathing behind your siding as this water
drains. Unfortunately, the wood trim on your house traps the moisture
between the sheathing and the trim, causing decay.

We often find that the response to this problem is to simply wrap the
face of the wood trim in aluminum. Unless other corrections are made,
this will only compound the decay, by further entrapping the water. Presuming
that a house wrap or felt paper is installed directly behind the vinyl
siding, before each piece of decaying wood is replaced, an aluminum drip
cap should be installed along the top of the wood. This “flashing” should
slip up behind the vinyl siding directly above the wood trim, and more
importantly should also slip behind the house wrap above the trim, and
form a cover with a drip edge over the top of the wood to direct water
out of the wall assembly. If there is no house wrap directly behind the
siding, complete removal of all siding and trim would be necessary for
correction of the problem.

I am interested in buying a house that has EIFS on the
exterior. I am aware that there have been problems with this product.
Can you explain what can be done to prevent any problems?

EIFS is the acronym for Exterior Insulation and Finish System. It consists
of a stucco finish applied over a foam insulation board and has been around
for a couple of decades. The product has been very popular in other parts
of the country, but is seen more often locally in commercial buildings.
Part of its popularity is that it provides a clean masonry-like appearance
and can be sculpted to reproduce classical exterior architectural details.

The primary problem is that any moisture that gets behind the foam board
insulation can become trapped inside the wall, cause rapid decay, and huge
repair costs. A class-action law suit was initiated in the 1990's, and
considerable redesign and improved installation guidelines were developed
at that time. The biggest changes included the requirement for a water
resistant membrane and a drainage mat between the foam board and the wood
wall sheathing. This allows any water that gets behind the foam to drain
out the bottom without causing any harm. Even so, the installation must
be done extremely carefully, and all flashing details around windows and
doors, roof intersections, etc. are critical. The manufacturers now provide
highly detailed installation guidelines to minimize errors.

Chances are, if the house was built before the mid-90's, there is no
drainage mat or secondary water intrusion barrier, greatly increasing the
likelihood of problems. In any case, it is wise to have a very thorough
inspection of the installation, and it may be appropriate to hire an inspector
with a moisture meter to more intensively evaluate the integrity of the
exterior finish than would occur during a standard home inspection.

In spite of the fact that our house has good air circulation
all around, the vinyl siding on the north side develops a green pond-scum
like growth in wet weather. What can we do about this? Is there a product
that we could spray on the siding to prevent this growth?

The green discoloration is caused by a common algae that finds the vinyl
siding on the shady north side of your house to be a suitable habitat for
growth. It is not harmful to the siding, but does provide a poor appearance
and can be a nuisance to remove. This algae is common in shady environments
in nature, and often grows on other exterior materials and finishes around
the house. Any overhanging trees or shrubs can aggravate the problem,
but are not necessary for the algae to grow. Washing with a mild detergent
solution, such as Spic and Span, and a long handled brush is usually sufficient
to remove the algae from vinyl. Wet down the entire wall first, apply
the solution with a garden sprayer, and clean from the bottom up to prevent
streaking. Hose down the wall thoroughly when done. Power washing, strong
cleaners or chlorine solutions are not normally necessary and may be harmful
to the siding or any plants below. For a list of vinyl cleaners specific
to various other stains we suggest visiting the Vinyl Siding Institute
website at www.vinylsiding.org.
Search “vinyl cleaners.”

Keeping the algae off of the siding for the long term can be more difficult.
There are products that claim to be able to resist algae, including vinyl
renewal products that contain antimicrobial polymers. We do not have any
personal experience with these to know what does or does not work. If
our readers have used any algae resistant coatings that they have found
to be particularly successful we will forward the information. If you
experiment with any such applications we recommend that you try a discreet,
out of the way area first, since these products are likely to affect the
sheen of your vinyl. If you choose to use a vinyl renewal coating, you
will be committing yourself to applying the product on at least one full
side, and possibly the whole house, to ensure an even appearance.

I have some fairly significant cracks in the brick exterior
walls of my house. The cracks start at the top corners of the windows
on each end of the house. What is causing this and what can I do
to stop it?

Cracks in exterior brick walls that start at the tops of window or door
openings are most often caused by swelling of the steel lintels that support
the brickwork above the openings. The lintel is usually an L shaped
piece of steel which provides a shelf for the brick to rest on as it spans
the opening. If the bottom flange of the steel lintel extends too
close to the face of the brick, or is otherwise exposed to moisture, the
steel will rust. As significant rusting occurs the metal expands. The
slow expansion produces enough force to lift the brickwork that is above
the window or door openings. This causes cracks to appear as the
bricks are lifted up off the masonry on either side of the openings. These
cracks are a very common occurrence, and usually do not result in major
damage. However, every effort should be made to protect the steel
from moisture, including caulking and painting the steel and possibly the
brick. It may be very difficult to determine the actual source of
the moisture, which could also be condensation from water vapor moving
through the walls from the interior, as well as wet masonry due to rain. So
be sure to take steps to control any excess moisture in the house which
might be contributing to the rusting. In the worst case, as the rusting
continues and the steel begins to seriously deteriorate, it may become
necessary to replace the lintels. This can be a very expensive proposition
if several window or door openings are involved. Being proactive
now to ensure that the steel stays dry may save a large expense later.